A copy machine was originally an analog system in which a page to be copied is illuminated by a light source to generate a latent image on a photosensitive drum. Toner is then applied to the drum and the toner is attracted and adheres to the latent image. A piece of blank copy paper is run past the photosensitive drum so that the latent image on the drum transfers to the copy paper. The image on the paper is then permanently fused on to the paper by a high temperature fuser. This type of copy machine is an analog machine because no digital image of the page is ever created.
With the advances of computers and scanners, a digital copier was introduced that scanned a page using a CCD into memory in digital format so that the page could be altered and reprinted more easily. A digital copier also made it much easier to create multiple sets of the same documents when the document is stored in memory. Recently, companies have begun to incorporate other features into these digital copiers. For example, a facsimile machine can be incorporated into a digital copier. In addition, if the digital copier is connected to a computer network, then the digital copier can also serve as a printer. All of these functions use the same scanning, control and printer units that are contained within the digital copier.
All of these machines, also known as reproduction machines, have an automatic document feeder that can be used to feed the reproduction jobs into the machine. In addition, for a multi-function digital machine, facsimile jobs can also be fed into the machine using the automatic document feeder.
Analog and digital reproduction machines and digital multi-function reproduction machines all have a problem that has never been fully resolved. Generally, a reproduction machine cannot sense that the user has incorrectly placed papers in the automatic document feeder. Typically, a reproduction machine has an automatic document feeder that either requires face-up original documents or face-down original documents. If a user places original documents face-up on a face-down automatic document feeder, then a reproduction machine will make blank copies that are of no use to the user.
There are several systems for sensing blank pages within a reproduction job and stopping the reproduction process. These systems stop a reproduction job whenever a blank page is detected. However, sometimes a user may intentionally place blank pages within a reproduction job in order to separate sections of a document. Any conventional blank page detection system can not differentiate between intentionally placed blank pages and blank pages caused by a reproduction job incorrectly placed on the automatic document feeder. In addition, many of these systems require that a separate sensor is used to generate the necessary data to determine if a blank page exists.